The present invention relates to a magnetic head apparatus for recording on and reproducing information from magnetic recording media, and more particularly, to a magnetic head apparatus, for a floppy disk drive system.
FIGS. 1 and 2 show an arrangement of a conventional magnetic head apparatus of a floppy-disk drive system, which is used to record on and reproduce information from a flexible magnetic recording disk. FIG. 1 is a plan view showing a sliding-contact surface of the apparatus to be in contact with the disk, and FIG. 2 is a front view of the apparatus of FIG. 1 as taken in the direction of arrow P. In FIG. 2, slider 1 shown in FIG. 1 is removed from the apparatus.
The magnetic head apparatus shown in FIGS. 1 and 2 is of a tunnel-erase type, as it is called. It comprises recording/reproducing head 2, erase head 3, non-magnetic isolation layer 4 for separating heads 2 and 3, and slider 1 formed of ceramics or the like. Head 2 is composed of recording/reproducing cores 21 and 22, formed of ferromagnetic material, and coil 23, wound around cores 21 and 22. Cores 21 and 22 are formed with recording/reproducing gap 24 and grooves 25 defining the width of gap 24. Gap 24 is adapted to generate leakage flux, in a recording mode, and detect magnetic fields from the disk, in a reading mode. Erase head 3 is composed of erase cores 31 and 32 formed of ferromagnetic material, and coil 33 wound around cores 31 and 32. Cores 31 and 32 are formed with erase gap 34 and grooves 35 defining the width of gap 34. Gap 34 serves to erase both side portions of information, which is recorded on the disk by recording/reproducing head 2.
Constructed in this manner, the prior art magnetic head apparatus of the floppy-disk drive system is located in position on the magnetic recording disk, by a stepping motor or other means, when it records or reproduces information. In the playback mode, however, the apparatus is liable to fall into a so-called off-track state, such that the recording/reproducing gap 24 of the recording/reproducing head 2 is positioned of a track on the disk where the information is recorded. In such a case, grooves 25 of head 2 run on an adjacent track, and serve as wider recording/reproducing gaps, thus producing side strokes. As a result, the signal-to-noise ratio of readout signals, delivered from coil 23 of head 2, is lowered.
Some of the latest floppy-disk drive systems use a magnetic head apparatus of a pre-erase type, as shown in FIG. 3. FIG. 3 is a plan view showing a sliding-contact surface of the apparatus, in which like reference numerals are used to designate like portions as shown in FIGS. 1 and 2, for simplicity of illustration. In the magnetic head apparatus of this type, erase gap 54 is located on the upper-course side of the track, with respect to the running direction, as compared with recording/reproducing gap 24. Thus, before data is written by recording/reproducing head 2, previously stored data is erased by erase head 3.
While recording/reproducing head 2 is reading data, in the pre-erase-type magnetic head apparatus, erase head 3 runs continually on a data track, so that intensive magnetic induction occurs in erase cores 51 and 52. If cores 51 and 52 are subjected to such substantial magnetic induction, lines of magnetic force are caused to reach recording/reproducing cores 21 and 22. As a result, the readout signals from coil 23 of head 2 are hampered by noises, so that their signal-to-noise ratio is lowered.
Also in the magnetic head apparatus of the tunnel-erase type, as shown in FIGS. 1 and 2, the off-track condition causes erase gap 34 of erase head 3 to run on an adjacent track. In this case, the intensity of those magnetic fields which, generated from data stored in the adjacent track, reach gap 34 increases, so that erase cores 51 and 52 are subjected to substantial magnetic induction. Thus, the signal-to-noise ratio of the readout signals, delivered from coil 23 of recording/reproducing head 2, is lowered. (Here it is to be noted that some magnetic induction can be caused without the off-track condition.)